Sheltered lower eulittoral rock subject to fully marine conditions characterised by a dense canopy of the wrack Fucus serratus. There is a wide range of associated species found on the surface of the rock underneath the canopy, including the barnacle Semibalanus balanoides, limpets Patella vulgata, winkles Littorina littorea, and even mussels Mytilus edulis can be present in cracks and crevices. These species are usually found in higher abundance further up on the shore. There may also be a number of other seaweeds present, including the red Corallina officinalis and Mastocarpus stellatus, the wrack Fucus vesiculosus and the green Enteromorpha intestinalis, Ulva lactuca or Cladophora rupestris, though these usually are present in low numbers if present at all. The sponge Halichondria panicea can be present underneath the F. serratus canopy in moist cracks or minor overhangs. Polychaetes such as Pomatoceros triqueter and Spirorbis spp. are present in their white calcareous tubes on the rock. Situation: This biotope usually occurs immediately below a Fucus vesiculosus-barnacle mosaic (unit A1.213) on moderately exposed shores or a dense canopy of F. vesiculosus (A1.313) or Ascophyllum nodosum (A1.3141) on sheltered shores; consequently low densities of these species (typically less than Frequent) may also occur in this biotope. The sub littoral fringe below on moderately exposed shores is dominated by the kelp Laminaria digitata (A3.211; A3.2112), while the kelp Laminaria saccharina may co-dominate on sheltered shores (A3.3131; A3.3121). Temporal variation: Fluctuations from year to year in the abundance of the F. serratus and the red seaweeds due to e.g. severe storms may convert this biotope into either A1.2141 or into a red seaweed dominated biotope on moderately exposed shores.